Numerous techniques have been developed through the years for measuring the adhesive bond strength of one material to another. In one type of test, a lap joint is formed from two substrates joined by a layer of adhesive material. Force is then applied to the substrates as close to parallel to the joint as possible, until failure occurs. This type of joint loading is thought to create a rather complex stress distribution since cleavage or peel may occur which may obscure adhesive shear properties. In another prior art test, a butt joint is formed and shear force is then applied to the adhesive joint. This type of test is reliable only if the test surfaces are very accurately aligned during testing; otherwise, unrestrained bending moments are introduced which affect the accuracy of the test.
Thus, a need has continued to exist for a simplified apparatus and method for measuring adhesive bond strength in which the stress applied to the test joint is limited essentially to shear stress, thus minimizing the effect of complex stress distributions on the desired measurement of adhesive shear strength.